Hydraulic control in a hydraulic system, especially for the operation of scrap cutters

ABSTRACT

The invention relates to hydraulic control in a hydraulic system for the operation of a machine tool such as a press for processing material of a certain type, especially for the operation of the scrap cutters. Said control allows for impact attenuation and combined rapid motion switching with load compensation and transfer of a hydraulic medium of a hydraulic cylinder for the movement of the other. According to the invention, said control comprises hydraulic media of a hydraulic cylinder for pre-control of a first main valve element ( 2.4.0 ), a second main valve element ( 2.7.0 ) and a third main valve element ( 3.7.0 ) which are functionally combined and a fourth valve ( 2.5 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 national phase application of InternationalApplication No. PCT/DE03/01022 having an international filing date ofMar. 27, 2003, and which claims priority to German Application No. DE102 23 267.9 filed May 24, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a hydraulic control in a hydraulic system forthe operation of a machine tool such as a press for processing materialof any desired type, such as presses and/or shears, in particular forshears for cutting metal scrap, such as “scrap shears”.

2. Prior Art

Machine tools such as presses essentially comprise

-   -   a column having at least one hydraulic cylinder guided and        fastened therein for driving a tamper, pressing or holding down        the material, toward a table and at least one hydraulic cylinder        guided and fastened therein for driving a tool, finally        processing and cutting the material, toward a fixed tool in said        table, and    -   a “hydraulic control” with tank, pumps, control blocks, valve        elements and nozzles and also the hydraulic medium for the        cyclic operation of the first and second cylinders.    -   a “hydraulic control” with tank, pumps, control blocks, valve        elements and nozzles and also the hydraulic medium for the        cyclic operation of the first and second cylinders.

It is known to provide means in the hydraulic control which generate adamping pressure for damping a “(cutting) impact” at least in one of thehydraulic cylinders at the end of its working stroke, such as, forexample, after the severing of metal scrap.

The general problematic nature of these (cutting) impacts has been knownfor a long time and has already been described in detail in publicationsDE 2808091A1, DE 2824176A1, DE 2909119A1, DE 3534467A1, DE 2221290C3, DE2928777C2, DE 3112393C2 and DE 19529134A1.

A useful and already known solution to the problem can be gathered fromthe preamble of the main claim of EP 0765203B1 (also published as U.S.Pat. No. 5,832,807), in which case this embodiment is to beadvantageously augmented by the characterizing features such as

-   -   the control pressure corresponding to the damping pressure can        be built up by inflow of control oil from the piston-side        cylinder space of the working cylinder via a bypass line into        the control space, and    -   a check valve which shuts off flow toward the piston-side        cylinder space is arranged in the bypass line.

The previously known hydraulic control can be effectively presented inthe following steps with regard to the outflow relevant to the dampingof the (cutting) impact (with reference to EP 0765203, also published asU.S. Pat. No. 5,832,807):

-   -   1. The cylinder descends with the cutter. A counter-pressure is        generated in the rod space 12 of the cylinder by means of a        pressure valve 54. The valve 54 interacts with a valve 31 as a        two-stage pressure-limiting valve, the valve 31 constituting the        main stage. A valve 38 is held by a spring in the position P-A,        since the control pressure in line 40 at this instant is still        low. The counter-pressure in the rod space during the downward        travel is necessary in order to hold the load attached to the        cylinder. Without this counter-pressure, the cylinder, due to        the weight of the piston rod and the attached load G, would        travel faster than predetermined by the pump quantity due to        gravitational effects. This would result in a vacuum in the        piston space 10, and this vacuum can cause problems with the        seals of the cylinder.    -   2. The cylinder, or the cutter, comes down on the material. The        pressure in the piston space 10 increases, since at this point        the cylinder is no longer moved. The pump continues to deliver        oil, which leads to a pressure increase in the piston space 10.        This pressure increase continues via the control line 62, the        valve 58 and the line 40 and leads to shifting of the valve 38        into position A-T. Accordingly, the control space of the valve        31 is connected via a nozzle 21 and the valve 38 to the tank;        and the valve 31 opens against the spring 66. As a result, the        previously required counter-pressure in the annular space 12 of        the cylinder collapses. The cylinder can now apply the full        desired force, defined by pressure times piston area, for        cutting the material. The cutter cuts the material when the        cutting force is reached.    -   3. The cutter is accelerated by the oil volume, acting as a        spring, in the piston space. Immediately after the cutting, the        pressure in the piston spaces 10 collapses through expansion. At        the same time, the valve 38, in the absence of control pressure,        shifts back into basic position P-A. The oil flow produced by        the accelerated cylinder is partly directed via the nozzle 36        and the valve 38 to the control space of the valve 31. The top        pressure on the annular-space side is limited, as in section        3.1, via the two-stage pressure-limiting valve (54/31). This        counter-pressure already constitutes a (cutting) impact damping.    -   4. As can be seen under 2, before cutting, the pressure in the        piston space 10 is high and the pressure in the annular space 12        is relieved toward the tank. Since the pressure in the piston        space 10 is now higher than in the annular space 12, oil flows        via the line 68 and the nozzles 70 and 36 and the check valve 72        from the piston space to the annular space and thus via the        valve 31 to the tank. This oil flow multiplied by the applied        pressure can adversely produce an unintentional power loss.    -    During the cutting (as described in 3), the pressure in the        piston space 10 collapses, at least partly. Since the pressure        in the piston space 10 has decreased and pressure has been        generated in the annular space by the accelerated cylinder,        there is the risk that no oil can flow via the line 68. The        pressure gradient then becomes opposed to the check valve.    -    The line 68 will therefore also lead to a mutual effect instead        of assisting damping. Furthermore, it is to be emphasized that        the valve 38 must first of all shift into the basic position for        the desired (cutting) impact damping to come into effect. The        precondition for this is that the pressure in the line 40 (thus        previously in the piston space 10) must have collapsed. Thus, in        particular cases, no oil can flow via the line 68 and        accordingly via the valve 38, since this at best requires        additional means on account of the circuit logic and the oil        required is fed via the nozzle 36 of the pilot control.

In addition, the (cutting) impact damping present per se is accordinglyto be assisted with simple means by the 4th step, which, however, doesnot appear possible without further means or may lead to furthercomplications.

The hydraulic controls already realized in industrial practice with thefeatures (in accordance with the steps 1 to 3 described above) definedin the preamble of abovementioned EP 0765203B1 (also published as U.S.Pat. No. 5,832,807), in particular in scrap shears, have proved to befunctional with regard to (cutting) impact damping; however, they are inneed of improvement in the context of a complex hydraulic problem. Withregard to the effectiveness of the technical means of the functiondescribed in step 4, this would only be partly realizable and only ifadditional means were to be used. This means at least a considerablecost outlay.

According to DE 4312283A1, the search for a solution approaches, suchas, for example, in large, but continuously working channel balingpresses, a control for a hydraulic heavy-duty actuator which is to becontrolled under load from an extended working position into a returnmovement, a hydraulically pressurized working space of the actuatorbeing connected to a return line of low pressure via a directionalcontrol valve, the valve position of which is set hydraulically via acontrol line which has at least one choke orifice.

In this case, a pressure-stabilizing delay element is connected inbetween the directional control valve and the choke orifice.

If the mode of operation of this control is analyzed with regard to themachine of the design mentioned at the beginning, valve operation forreducing relief impacts is certainly presented and a bracketed pressurefrom a system is reduced as smoothly as possible in order to reduceimpacts extending into the tank line.

However, the rapid buildup of a counter-pressure in a cylinder and thenalso thus the limiting of this counter-pressure by this measure is notpossible.

An approach to the solution of the present problem does not follow fromthis disclosure.

The aim of building up a counter-pressure as rapidly as possible and oflimiting it in a cylinder of the machines of the generic type, takinginto account their specific mode of operation, also cannot be achievedby the solution according to EP 1186783A1. According to this patent,only the oil flowing off from one cylinder is used for generallyapplying pressure to and driving a second cylinder. This effect isassumed to be known in order to actually fulfill the basic function ofthe hydraulic control in these machines.

It can therefore be stated that the problem of the (cutting) impactdamping by means of hydraulic control for presses, and in particularshears for cutting metal scrap, defined at the beginning has hithertonot been solved comprehensively within the scope of the entire hydraulicsystem.

Thus, the volume of the hydraulic medium provided by the pumps inhydraulic controls for machine tools such as presses, and in particularshears for cutting metal scrap, constitutes a limit to the speed of thesequences of hydraulic cylinders, since the hydraulic medium flowing tothe tank remains unused as a rule. There is also that fact thatperpendicularly working hydraulic cylinders, such as in presses orshears, with attached masses of, for example, tools impose specialdemands on the hydraulic control. If the annular space of the cylinderis simply relieved toward the tank during the downward travel of thiscylinder, the extension being effected downward, the piston of thecylinder could descend due to the dead mass and the attached load andcould possibly run in advance of the action of the pumps. This has anadverse effect at least on the service life of the cylinder seals andmay also be disadvantageous for the entire hydraulic system.

Finally, in conventional hydraulic controls for uses described above,with the simultaneous upward movement of two cylinders, the cycle timeof the processing operation, such as after the shearing for example, isconsiderably restricted.

BRIEF SUMMARY OF THE INVENTION

These problems, in their entirety, associated per se with thecorresponding hydraulic system, such as

-   -   (cutting) impact damping with simple means and/or    -   rapid-motion control with load compensation and/or    -   oil transfer with increase in output        as a complex hydraulic control of the application described at        the beginning, give rise to the definition of the object        according to the invention.

The object of the invention is to provide a hydraulic control in ahydraulic system for the operation of a machine tool such as a press forprocessing material of any desired type, in particular for scrap shears,which, in a functional combination of partly known features,

-   -   produces (cutting) impact damping with little constructional        outlay in terms of hydraulic means, with which (cutting) impact        damping the maximum counter-pressure on the annular-space side        of the cylinder can be set at a higher level than in        conventional solutions for generating a counter-pressure, and/or    -   links rapid-motion control with load compensation and uses the        hydraulic medium flowing off in a conventional manner to the        tank, and/or    -   reduces the cycle time and increasing increases the output of        the machine, during the simultaneous upward movement of two        cylinders, by using the outflowing hydraulic medium of one of        the cylinders for driving or moving the other cylinder at the        same pump delivery quantity.

In effect, a complex hydraulic control in the hydraulic system for theoperation of machine tools, such as presses, and in particular scrapshears, is provided which, in addition to the solved problem offunctionally simple but functionally fully effective impact damping,increases the output rates of the material to be processed withoutincreasing the installed capacity and the construction cost, whereby theoperator can also be provided with a machine having a higher energyservice value.

The invention is explained with reference to an exemplary embodimentaccording to the scheme of the hydraulic circuit for the operation ofscrap shears with the aid of the drawings.

BRIEF DESCRIPTION OF THE DRAWING

The circuit corresponding to the hydraulic system according to theinvention is schematically shown in the drawing. In the drawing, theline _._. outlines the actual control.

DETAILED DESCRIPTION OF THE INVENTION

In the drawing a first hydraulic cylinder 1.1 which drives a tool, suchas a cutter slide with the cutter 1.1.3 which cuts material and a secondhydraulic cylinder 1.2 which drives a further tool, such as a tamper1.2.3 for holding down the material to be cut, are shown in a simplifiedmanner. The cylinders 1.1 and 1.2 have bottom spaces 1.1.2 and 1.2.2,respectively and annular spaces 1.1.1 and 1.2.1, respectively. Thehydraulic inlets or outlets for the hydraulic medium of the bottomspaces 1.1.2, 1.2.2 in both cylinders 1.1 and 1.2 are designated by Aand the inlets and outlets for the hydraulic medium of the annularspaces 1.1.1, 1.2.1 are designated by B. T symbolizes the line to a tankor reservoir (not shown), and P1 and P2 symbolize the connections to thepressure lines and the pumps (not shown).

The basic circuit of the hydraulic control for the operation of thescrap shears is first of all preset with a second valve 2.2 between thebottom space 1.1.2 of the first hydraulic cylinder 1.1 and the tank orreservoir T and with a third valve 2.3 between the annular space 1.1.1and the connection to the pressure supply P1.

Furthermore, a fifth valve 3.1 is provided between the bottom space1.2.2 of the second hydraulic cylinder 1.2 and the connection to thepressure supply P2 and a sixth valve 3.2 is provided between the bottomspace 1.2.2 and the tank or reservoir T.

Finally, a seventh valve 3.3 is arranged between the annular space 1.2.1and the connection to the pressure supply P2 and an eighth valve 3.4 isarranged between the annular space 1.2.1 and the tank or reservoir T.

The function of the hydraulic control, which acts in the hydraulicsystem in accordance with the definition of the object, is explained inmore detail in subsections I, II and III below.

I. Functional Part—(Cutting) Impact Damping

In scrap shears, the cutter slide 1.1.3 with the connected piston of thecylinder 1.1 is accelerated after the shearing of the material. Thecause of the acceleration is a high pressure in the bottom space 1.1.2of the cylinder 1.1 up to just before the cut occurs. The compressedvolume of the hydraulic medium acts as an energy store. The compressedhydraulic medium accelerates the cylinder 1.1 with cutter slide 1.1.3.Before the cutting or shearing, the annular space 1.1.1 of the cylinder1.1 is relieved. In order to counteract the acceleration of the cutterslide 1.1.3 and a resulting hydraulic impact, a counter-pressure isgenerated in the annular space 1.1.1 of the cylinder 1.1, thiscounter-pressure being suitable for damping the hydraulic impact.

At the instant directly before the material is cut through, a firstvalve 2.1 (not previously mentioned) between the bottom space 1.1.2 andthe connection to pressure supply P1 and a pilot-control valve 2.4.3(not previously mentioned) are in an operated position. As a result, thebottom space 1.1.2 of cylinder 1.1 is connected via the first valve 2.1to the connection to the pressure supply P1, which is fed by hydraulicpumps (not shown). The annular space 1.1.1 of the first hydrauliccylinder 1.1 is relieved toward the tank (not shown) via a first mainvalve element 2.4.0 with a cap 2.4.1.

The drive motors (not shown) of the hydraulic pumps are protectedagainst overload by a suitable output limit of the pumps. This outputlimit sets a lower delivery flow rate of the hydraulic medium at highpressures, so that the product of pressure and volumetric flow, whichproduct corresponds to the hydraulic power, remains virtually constant.Accordingly, the volumetric flow rate of the hydraulic medium is low athigh pressures compared with the volumetric flow rate at low pressures.The speed of the first hydraulic cylinder 1.1 is therefore also lower athigh pressures compared with that at low pressures.

The opening stroke of the first main valve element 2.4.0 is adapted byan integrated spring (not designated) to the volumetric flow via therelevant valve.

During an abrupt rapid movement of the piston of the first hydrauliccylinder 1.1 (as described above), the first main valve 2.4.0 is delayedin its opening movement by a nozzle 2.4.1.1 essential to the invention.At the same time, the pressure in the annular space 1.1.1 of thecylinder 1.1 is set by the pressure valve 2.4.2, as pilot control of thefirst main valve element 2.4.0, to the pressure set at the pressurevalve 2.4.2. The delay in the opening of the second main valve element2.4.0 is surprisingly sufficient for generating a limitedcounter-pressure and thus for (cutting) impact damping.

Consequently, with simple means and in an advantageous manner, themaximum counter-pressure on the annular space side 1.1.1 of the firsthydraulic cylinder 1.1 can be set higher than in the previously knownsolutions for generating a counter-pressure, whereby this partialsolution can also be realized with less outlay in terms of construction.

II. Functional Part—Rapid-Motion Control Linked with Load Compensation

The delivery volume made available by the pumps has hitherto constituteda limit in the cylinder speed in hydraulic scrap shears, in which casethe hydraulic medium flowing in a conventional manner to the tank is nowto be utilized. Furthermore, perpendicularly working hydraulic cylinders1.1 and 1.2 with attached loads due to the weight of the tools, such ascutter slide 1.1.3 and tamper 1.2.3, are to be controlled in a specialmanner.

If the annular spaces 1.1.1 and 1.2.1 were simply to be relieved towardthe tank T during the downward travel of the cylinders 1.1 and 1.2, inthe course of which the extension is effected downward, the respectivepiston of the hydraulic cylinders 1.1 and 1.2 could descend due to thedead weight caused by the attached load of said tools and could move inadvance of the action of the hydraulic pumps. This would have adverseeffects on the service life of the cylinder seals.

As a countermeasure during the downward travel in the respective annularspace 1.1.1, 1.2.1, a pressure is to be generated which is large enoughto compensate for the attached load, such as the tools for example. Ithas been determined in pilot tests that a pressure difference betweenannular spaces 1.1.1, 1.2.1 and bottom spaces 1.1.2 and 1.2.2 of thehydraulic cylinders 1.1, 1.2 is suitable for compensating for the loaddue to weight. At the same time, the hydraulic medium flowing off at Bon the annular-space side is to be used for the purposes of aconventional rapid-motion control.

By means of the circuit according to the drawing, both requirements arerealized in a combined manner by virtue of the fact that a second mainvalve element 2.7.0 with a cap 2.7.1, an intermediate plate 2.7.2, apressure valve or choke (nozzle) 2.7.3 and a directional control valve2.7.4 and, similarly, a third main valve element 3.7.0 with a cap 3.7.1,an intermediate plate 3.7.2, a pressure valve or choke (nozzle) 3.7.3and a directional control valve 3.7.4 are arranged according to theinvention.

These circuits are especially advantageous for downward movements with alow counterforce on the hydraulic cylinders 1.1, 1.2.

The respective valve combination, from the second and third main valveelement 2.7.0, 3.7.0, interacts with a pilot-control arrangement whichis formed by the cap 2.7.1, 3.7.1, intermediate plates 2.7.2, 3.7.2,pressure valves or chokes (nozzles) 2.7.3, 3.7.3 and the directionalcontrol valves 2.7.4, 3.7.4.

This pilot-control arrangement, in the linking according to the drawing,in combination with the respective main valve element 2.7.0, 3.7.0,constitutes a controllable pressure valve having a check function, inwhich case the pressure on the annular-space side can be set relative tothe pressure on the piston side so as to be matched to the hydrauliccylinders 1.1, 1.2.

An alternative combination of a separate rapid-motion valve withload-compensation function could constitute an optimum solution from theenergy point of view.

III. Functional Part—Transfer of the Hydraulic Medium

During the simultaneous upward movement of two cylinders 1.1, 1.2 asdescribed above, the outflowing hydraulic medium of one of the cylinders1.1, 1.2 is to be used for moving the other cylinder 1.1, 1.2. Thequantity of hydraulic medium which is thus obtained compared withconventional concepts considerably reduces the cycle time of the press,and in particular of scrap shears, at the same pump delivery quantity.

The circuit according to the invention produces an increase in outputcompared with conventional concepts. The circuit for such use of theoutflowing hydraulic medium is realized according to the invention by afourth or switch valve 2.5 between the bottom space 1.2.2 of cylinder1.2 and the annular space 1.1.1 of cylinder 1.1. In the circuit shown,the cylinders 1.1, 1.2 driven via the outflowing medium can beadditionally driven with further pumps.

INDUSTRIAL APPLICABILITY

Although the invention is specifically explained with regard to thehydraulic system of scrap shears, it can be applied to the operation ofmachine tools such as presses of the generic type mentioned at thebeginning in which, to all intents and purposes, the complex problem ofimpact damping, rapid-motion control with load compensation, and/ortransfer of the hydraulic medium between at least two hydrauliccylinders is to be solved.

LIST OF DESIGNATIONS

-   1.1 First hydraulic cylinder for driving a tool such as 1.1.3-   1.1.1 Annular space-   1.1.2 Bottom space-   1.1.3 Cutter slide with cutter-   1.2 Second hydraulic cylinder for driving a tool such as 1.2.3-   1.2.1 Annular space-   1.2.2 Bottom space-   1.2.3 Tamper for holding down the material-   2.1 First valve between bottom space 1.1.2 and P1-   2.2 Second valve between bottom space 1.1.2 and tank T-   2.3 Third valve between annular space 1.1.1 and P1-   2.4.0 First main valve element-   2.4.1 Cap-   2.4.1.1 Nozzle-   2.4.2 Pressure valve-   2.4.3 Pilot-control valve-   2.5 Fourth or switch valve between bottom space 1.2.2 and annular-   space 1.1.1-   2.7.0 Second main valve element-   2.7.1 Cap-   2.7.2 Intermediate plate-   2.7.3 Pressure valve or choke (nozzle)-   2.7.4 Directional control valve-   3.1 Fifth valve between bottom space 1.2.2 and P2-   3.2 Sixth valve between bottom space 1.2.2 and tank T-   3.3 Seventh valve between annular space 1.2.1 and P2-   3.4 Eighth valve between annular space 1.2.1 and tank T-   3.7.0 Third main valve element-   3.7.1 Cap-   3.7.2 Intermediate plate-   3.7.3 Pressure valve or choke (nozzle)-   3.7.4 Directional control valve-   A Inlet/outlet, bottom space-   B Inlet/outlet, annular space-   P1 Connection to the pressure supply-   P2 Connection to the pressure supply-   T Connection to the tank or reservoir

1. A hydraulic control system for operating a machine tool forprocessing material, comprising at least one hydraulic cylinder having abottom space (1.1.2) and an annular space (1.1.1), and hydraulic meansfor setting a higher maximum counter-pressure in the annular space(1.1.1) for impact damping, said hydraulic means comprising: a firstmain valve element (2.4.0) disposed in a fluid flow line from saidannular space (1.1.1) to a hydraulic fluid reservoir (T), a nozzle(2.4.1.1) for delaying opening movement of the first main valve element(2.4.0) in case of sudden rapid movement of said cylinder; and apressure valve (2.4.2) for simultaneously limiting, as pilot control ofthe first main valve element (2.4.0), the pressure in the annular space(1.1.1) in said cylinder (1.1) to a pressure set at the pressure valve(2.4.2); said nozzle (2.4.1.1) and pressure valve (2.4.2) causing thegeneration of a limited counter-pressure for impact damping in saidannular space (1.1.1), said impact damping being assisted by apilot-control valve (2.4.3) controlling the first main valve element(2.4.0).
 2. A hydraulic control system for operating a machine tool forprocessing material having at least two hydraulic cylinders (1.1, 1.2)each having a bottom space (1.1.2, 1.2.2) and an annular space (1.1.1,1.2.1), and comprising: a. hydraulic means for setting a higher maximumcounter-pressure in the annular space (1.1.1) of a first (1.1) of saidat least two hydraulic cylinders for impact damping including: a firstmain valve element (2.4.0) disposed in a fluid flow line from saidannular space (1.1.1) to a hydraulic fluid reservoir (T), a nozzle(2.4.1.1) for delaying opening movement of the first main valve element(2.4.0) in case of sudden rapid movement of said cylinder (1.1); and apressure valve (2.4.2) for simultaneously limiting, as pilot control ofthe first main valve element (2.4.0), the pressure in the annular space(1.1.1) in said first cylinder (1.1) to a pressure set at the pressurevalve (2.4.2); said nozzle (2.4.1.1) and said pressure valve (2.4.2)causing the generation of a limited counter-pressure for impact dampingin said annular space (1.1.1), said impact damping being assisted by apilot-control valve (2.4.3) for controlling the first main valve element(2.4.0); b. rapid-motion control and load compensation means utilizingthe hydraulic fluid flowing from the annular spaces (1.1.1, 1.2.1) ofthe hydraulic cylinders (1.1, 1.2) to a hydraulic fluid reservoir (T),said rapid-motion control and load compensation means comprising: asecond main valve element (2.7.0) disposed in a fluid flow line in fluidcommunication with the bottom space (1.1.2) and the annular space(1.1.1) of said first cylinder (1.1), and a first pilot-controlarrangement controlling the second main valve element (2.7.0) to set thepressure in the annular space (1.1.1) of first said cylinder (1.1) toexceed the pressure of the bottom space (1.1.2) thereof by apredetermined value, and a third main valve element (3.7.0) disposed ina fluid flow line in fluid communication with the bottom space (1.2.2)and the annular space (1.2.1) of the second cylinder (1.2), and a secondpilot-control arrangement controlling said third main valve element(3.7.0) to set the pressure in the annular space (1.2.1) of said secondcylinder (1.2) to exceed the pressure in the bottom space (1.2.2) ofsaid second cylinder (1.2) by a predetermined value; and c. means usingthe outflowing hydraulic fluid from one (1.2) of said at least twohydraulic cylinders for driving the other (1.1) of said at least twohydraulic cylinders at the same pump delivery rate, for reducing thecycle time and for increasing the output of the machine tool duringsimultaneous upward movement of said cylinders (1.1, 1.2), said meansincluding a switch valve (2.5) adapted to place the bottom space (1.2.2)of said one (1.2) of said cylinders in fluid communication with theannular space (1.1.1) of the other cylinder (1.1) so that the outflowinghydraulic medium of said one cylinder (1.2) is usable for moving theother cylinder (1.1).
 3. The hydraulic control system as claimed inclaim 2, further including at least one accumulator connected to atleast one of said pressure valve (2.4.2) and said pilot-control valve(2.4.3) of said first main control valve element (2.4.0).
 4. Thehydraulic control system as claim in claim 2, wherein said second andthird main valve elements (2.7.0, 3.7.0) are provided with pressurevalves or chokes (2.7.3, 3.7.3) for setting the pressure differencebetween said annular spaces (1.1.1, 1.2.1) of said cylinders (1.1, 1.2)and the hydraulic fluid reservoir (T).
 5. The hydraulic control systemas claimed in claim 2, wherein in that at the instant before suddenrapid movement of said one cylinder (1.1) a first valve (2.1) betweenthe bottom space (1.1.2) and the reservoir (T) and said pilot-controlvalve (2.4.3) are in an operated position.
 6. The hydraulic controlsystem as claimed in claim 5, wherein the bottom space (1.1.2) of saidone cylinder (1.1) is connectable by the first valve (2.1) to a pressurefluid supply line (P1).
 7. The hydraulic control system as claimed inclaim 2, wherein the annular space (1.1.1) of said one cylinder (1.1) isadapted to be relieved toward the hydraulic fluid reservoir via thefirst main valve element (2.4.0).
 8. The hydraulic control system asclaimed in claim 2, wherein the opening stroke of the first main valveelement (2.4.0) is adaptable by an integrated spring to the volumetricflow of the hydraulic medium through the first main valve element(2.4.0).
 9. The hydraulic control system as claimed in claim 2, whereinthe first and second pilot-control arrangements are each provided with acap, an intermediate plate, pressure valve or choke, and a directionalcontrol valve (2.7.1, 2.7.2, 2.7.3, 2.7.4 and 3.7.1, 3.7.2, 3.7.3,3.7.4) and form, in combination with the respective main valve elements(2.7.0, 3.7.0), controllable pressure valves with check function to setthe pressure in the annular spaces (1.1.1, 1.2.1) relative to the bottomspaces (1.1.2, 1.2.2) of the cylinders (1.1, 1.2) or the pressure in theannular spaces of the cylinders (1.1, 1.2) relative to the reservoirpressure.
 10. The hydraulic control system as claimed in claim 5,wherein a second valve (2.2) is arranged between the bottom space(1.1.2) of the first cylinder (1.1) and the reservoir (T), a third valve(2.3) is arranged between the annular space (1.1.1) of the firstcylinder (1.1) and a first pressure fluid supply line (P1), a fifthvalve (3.1) is arranged between the bottom space (1.2.2) of the secondcylinder (1.2) and a second pressure fluid supply line (P2), a sixthvalve (3.2) is arranged between the bottom space (1.2.2) of the secondcylinder (1.2) and the reservoir (T), a seventh valve (3.3) is arrangedbetween the annular space (1.2.1) of the second cylinder (1.2) and thesecond pressure fluid supply line (P2), and an eighth valve (3.4) isarranged between the annular space (1.2.1) of the second cylinder (1.2)and the reservoir (T).
 11. The hydraulic control system as claimed inclaim 10, further including software for controlling the functionsimpact damping rapid motion control with load compensation, and use ofthe outflowing medium of one of the cylinders for driving the other bymeans of said first, second and third valves (2.1, 2.2, 2.3); the firstmain valve element (2.4.0) with cap (2.4.1), nozzle (2.4.1.1), pressurevalve (2.4.2), and pilot control valve (2.4.3); the switch valve (2.5)forming a fourth valve; the second and third main control valve elements(2.7.0, 3.7.0), each provided with a cap (2.7.1, 3.7.1), an intermediateplate (2.7.2, 3.7.2), pressure valve (2.7.3, 3.7.3) and directionalcontrol valve (2.7.4, 3.7.4); and the fifth, sixth, seventh and eighthvalves (3.1, 3.2, 3.3, 3.3 and 3.4).
 12. The hydraulic control system asclaimed in claim 1, further including at least one accumulator connectedto at least one of said pressure valve (2.4.2) and said pilot controlvalve (2.4.3).
 13. The hydraulic control system as claimed in claim 1,further including a valve (2.1) between the bottom space (1.1.2) andsaid reservoir (T), wherein at the instant before the sudden rapidmovement of said cylinder (1.1) said valve (2.1) and said pilot-controlvalve (2.4.3) are in an operated position.
 14. The hydraulic controlsystem as claimed in claim 13, wherein the bottom space (1.1.2) of saidcylinder (1.1) is connectable via the valve (2.1) to a pressure fluidsupply line (P1).
 15. The hydraulic control system as claimed in claim1, wherein the annular space (1.1.1) of said cylinder (1.1) is adaptedto be relieved towards said reservoir (T) via the first main valveelement (2.4.0).
 16. The hydraulic control system as claimed in claim 1,wherein the opening stroke of the first main valve element (2.4.0) isadaptable by an integrated spring to the volumetric flow of thehydraulic fluid via the first main valve element (2.4.0).